Generally, lighting is controlled using pulse width modulation (PWM) signals. When two or more lights are controlled, a PWM signal is generated for each light, and a power supply device supplies power to each light according to the PWM signal. However, according to conventional lighting control technique, an overlapping section between PWM signals causes a difference between the maximum supply power and the minimum supply power to increase in a power supply device. Thus, the life of components of the power supply device may be shortened, and noise may be generated.